The Resonance Triangle of /a/: Geometric Symmetry in Human Oral Anatomy

This study proposes a new anatomical-phonetic hypothesis: when pronouncing the open vowel /a/, the oral cavity forms an equilateral triangle defined by the bilateral third molar roots of the mandible and the posterior nasal spine of the maxilla. This triangular geometry reflects a biomechanical configuration optimized for resonance stability and vocal projection. The model highlights a previously unnoted geometric aspect of vowel production and offers new insights for phonetics, vocal pedagogy, and speech modeling. Author : Tetsuo Konno(今野哲夫)